In recent years, increasing attention has been paid to the application of Vertical Axis Wind Turbines (VAWTs) for microeolic power generation. Prompted by a market research in this sector, which showed an interest in developing a family of VAWTs for these purposes, a design process has been carried out at the Department of Energy Engineering of Florence. This paper describes the steps in this design process with particular reference to two Darrieus turbines, with a nominal power of 400 W and 1 kW, respectively. In order to predict the performance of the machines, three different numeric codes have been developed in MatLab®; the main features of the codes are provided. An optimizing process has been also performed on the blade airfoil with a CFD code to increase its performance for the operating Reynolds numbers. Starting from technological constrains (such as minimum blade thickness, maximum rotational speed, generator capability, etc.) the two turbines have been finally designed with the most advanced version of the developed code.